PROJECT SUMMARY (See instmctions): As a result of the already complete GWAS studies, outstanding loci for further functional characterization have already been identified. In particular, and as described in more detail below, the rs1696698 SNP in the nicotinic acetycholine receptor unit 5 (CHRNAS) influences risk for lung cancer and affects smoking behavior and has also been shown to affect the activity of the multimeric nicotinic receptor in vitro. While this variant has important effects on nicotine receptor activity, extensive studies in Caucasian and African-American populations show that it is not the only variant influencing lung cancer risk and smoking behavior in the region of chromosomes 15q24-25.1, and the effects of rsl 696698 remain poorly characterized. Therefore, we plan further studies to define effects of variations in this region on nicotinic receptor activity, expression of the genes in the region and on effects of variations on cellular phenotypes relating to cancer development and progression. In addition, GWAS studies have identified excellent candidates on chromosomes 5p and 6p that wanrant further detailed analyses. For aim 1 of area 2 we propose to characterize methylation for the loci that have been identified. We also propose additional cellular phenotype based assays for loci that have been identified and the evaluation of phenotypes in existing animal models. Aim 2 of area 2 will detemiine the effect of CHRNA3/CHRNA5 polymorphisms on the biophysical and pharmacological properties of neuronal nicotinic acetylcholine receptors (nAChRs). We also propose additional cellular phenotype based assays for loci that have been identified and the evaluation of phenotypes in existing and new animal models (Aims 3 &4 of area 2)..